The Vatican City was filled with well-wishers and world leaders as Pope Francis began the formal start of his papacy. Tuesday morning he offered a passionate pledge to serve “the poorest, the weakest, the least important,” striking the same tones of humility as have marked the days since he was elected last week.

On a raised and canopied throne on a purple platform looking out from St. Peter’s Basilica to the huge piazza in front of it, the pope enjoined those in temporal power to protect the world and “not allow omens of destruction and death to accompany the advance of this world.”

“Today, too, amid so much darkness, we need to see the light of hope and to be men and women who bring hope to others,” he added to frequent applause from some among the tens of thousands people cramming the square and the broad avenue leading to it from the River Tiber.

Clearly defining his vision of his own role, he quoted from scriptural texts to say that as Bishop of Rome, he was endowed with “a certain power.”

But he went on: “Let us never forget that authentic power is service and that the pope too, when exercising power, must enter ever more fully into that service which has its radiant culmination on the Cross.”

“He must be inspired by the lowly, concrete and faithful service which marked St. Joseph and, like him, he must open his arms to protect all of God’s people and embrace with tender affection the whole of humanity, especially the poorest, the weakest, the least important, those whom Matthew lists in the final judgment on love: the hungry, the thirsty, the stranger, the naked, the sick and those in prison.”

His words, referring to St. Joseph, on whose day the inauguration fell, found an echo. “This is why we are all here, his warmth,” said Andreina Baldi, 58, a housewife from Rome, the end of Francis’ homily.

“He just said that we should all open our arms to welcome God’s people, anybody, the poor, the youngest, those in jail. And he is already doing so. He wouldn’t stop kissing a baby in his tour on the pope mobile earlier, right here, in front of me,” she said.

At 76, Francis was elected last Wednesday as the 266th pontiff of the Roman Catholic Church to replace the far more formal and reserved Benedict XVI, 85, who became the first pope in 600 years to resign, citing poor health and failing strength.

The weather proved appropriate and sunny as the Pope took his place signifying what many are believing to be a new reign of change from within the Catholic church.

For most of the people assembled in St. Peter’s Square, the first glimpse of Francis on Tuesday came when he arrived among the faithful gathered below the soaring facade of St. Peter’s, standing in the rear of a white open-air vehicle rather than a covered version of the traditional popemobile protected by bulletproof glass.

He wore simple white robes, halted to kiss a baby in the crowd and walked among the faithful. At one point, he gave supporters a thumbs-up sign, drawing laughter. He also stopped to kiss a disabled man in the crowd and people in the square said he seemed informal and relaxed. Many cried “Viva il Papa” — “long live the pope.”